This invention relates to the addition of alkyl groups to halodisilanes to produce more highly alkylated organosilanes and organodisilanes.
In the silicones industry organosiloxanes are prepared from the hydrolysis of organohalosilanes. The predominant starting organohalosilanes are the diorganodihalosilanes which produce diorganopolysiloxanes materials utilized in fluids, high-molecular weight linear polymers used in silicone elastomers, and the like. Organohalosilanes are primarily produced by the direct reaction of silicon and organic halides, as first disclosed by Rochow and his co-workers in the 1940's. The direct reaction can be controlled so that the predominant component is the diorganodihalosilane. However, other products of lower commercial value are also produced. These other products include tetrahalosilanes, organotrihalosilanes, helodisilanes, organohalodisilanes, and similar more highly halogenated species. It would be advantageous if such highly halogenated species could be efficiently converted to the more useful diorganodihalosilanes. Additionally, the demand for silanes of higher organic content such as triorganohalosilanes is often greater than the supply from the direct reaction. Further, more highly alkylated disilanes are chemical intermediates of interest.
As an early example of the preparation of organosilicon compounds using metallic reagents, Kipping and Dilthey both demonstrated the alkylation of tetrachlorosilane via reaction with an organ0 magnesium halide, the well-known Grignard process.
Hurd, J. Am. Chem. Soc. (1945), vol. 67, pp. 1545-1548, and Hurd, U.S. Pat. No. 2,403,370, issued July 2, 1946, disclose the alkylation of tetrachlorosilane and various methylchlorosilanes by passing the vapors of these chlorosilanes together with an alkyl halide over finely divided aluminum, zinc, or other reactive metal at elevated temperatures of 300.degree. to 500.degree. C. Hurd discloses that a reaction occurs under these conditions in which chlorine groups on the chlorosilane are replaced by alkyl groups.
Artes et al., U.S. Pat. No. 4,400,528, issued Aug. 23, 1983, discloses a process for methylating silicon compounds containing halogen and at least 2 silicon atoms with tetramethylsilane in the presence of at least one organoaluminum compound in the presence of a hydrogen-containing silane. The process disclosed by Artes et al. is a liquid phase reaction.